Introduction to OData

The example app for this section consumes live eBay data, which is exposed using the Open Data Protocol (OData). OData is a web protocol for querying and updating data. It defines operations on resources using HTTP verbs (PUT, POST, UPDATE, and DELETE), and it identifies those resources using a standard URI syntax. Data is transferred over HTTP using the AtomPub or JSON standards. For AtomPub, the OData protocol defines some conventions on the standard to support the exchange of query and schema information.

For in-depth information on the OData standard, visit http://odata.org.

A key advantage of the OData protocol is its accessibility by a broad range of clients. Client libraries are available for Windows Phone, iPhone, Silverlight, PHP, AJAX/Javascript, Ruby, and Java.

An OData service can be implemented on any server that supports HTTP. The .NET implementation is supported through WCF Data Services, which is a .NET Framework component that used to be known as ADO.Net Data Services (codename Astoria). WCF Data Services provides a framework for creating OData web services and includes a set of client libraries (one for the desktop CLR, and one for the Silverlight CLR) for building clients that consume OData feeds.

Services that expose their data using the OData protocol are referred to as OData producers, and clients that consume data exposed using the OData protocol are referred to as consumers. OData producers allow CRUD operations to be performed using query string parameters. The odata.org website provides a list of current producers and consumers. Among the producers, there are applications such as SharePoint 2010, Windows Azure Storage, and IBM WebSphere, as well as several live OData services such as the eBay data service, which is used in the sample app.